Double contact disconnect switch structure with contacts in gastight sealed relationship with a tubular support

ABSTRACT

A disconnect switch for use in compressed-gas switch installations comprises two gaps arranged electrically in series within a tubular casing. Each gap which is designed for the rated isolation voltage is constituted by a fixed contact member and a movable contact member, the two movable contact members are arranged for movement in opposite directions longitudinally of themselves by means of a common actuating mechanism to engage and be disengaged from their respective fixed contact members, the two movable contact members are supported within one section of the casing established by means of a transversely placed bulkhead of insulating material, and the two stationary contact members are located in adjacent sections of the casing.

United States Patent Inventor Gerhard Koerner Schriesheim, Germany Appl. No. 713,448 Filed Mar. 15, 1968 Patented Feb. 9, 1971 Assignee Aktiengesellschaft Brown Boveri & Cie

Baden, Switzerland a joint stock company Priority Apr. 6, 1967 Germany B91944 DOUBLE CONTACT DISCONNECT SWITCH STRUCTURE WITH CONTACTS IN GASTIGHT SEALED RELATIONSHIP WITH A TUBULAR SUPPORT Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A. Vanderhye AttomeyPierce, Scheffler & Parker ABSTRACT: A disconnect switch for use in compressed-gas switch installations comprises two gaps arranged electrically in series within a tubular casing. Each gap which is designed for the rated isolation voltage is constituted by a fixed contact member and a movable contact member, the two movable contact members are arranged for movement in opposite directions longitudinally of themselves by means of a common actuating mechanism to engage and be disengaged from their respective fixed contact members, the two movable contact members are supported within one section of the casing established by means of a transversely placed bulkhead of insulating material, and the two stationary contact members are located in adjacent sections of the casing.

nousuz CONTACT DISCONNECI swrrcrr STRUCTURE WITH CONTACTS IN GASTIGHT RELATIONSHIP WITH A TUBULAR SUPPORT This invention relates to an improvement in an electrical switch with two gaps arranged electrically in series forming a double disconnect section, for compressed-gas insulated switch installations whose casings are composed of tubular elements.

In the construction of compressed-gas insulated switch installations, the ease of assembly and, owing to the need for maintenance, of dismantling is a primary consideration. In order to avoid extensive operational disturbances, it will be generally endeavored to shut down the smallest possible section of the installation during maintenance work. Consequently, the disconnecting devices in an installation of this kind constitute a very important feature, particularly since the servicing operations can be carried out only after the plant sections concerned have been freed of compressed gas. This also raises the question of sealing, since it must be remembered that the insulating and disconnecting characteristics unfavorably change when the gas pressure falls. In addition, provision must be made for earthing the disconnected section. These requirements have led to the use hitherto of disadvantageous double bulkhead walls and complicated earthing devices.

Moreover, the known arrangements are in many cases too bulky, time consuming with regard to servicing and repair work and therefore do not fulfill their purpose in the desired manner (see in this connection Brown, Boveri Mitt., 1966, No. 4/5, ETZ-A 1965, No. 7, and Siemens-Zeitschrift 1966, No. 4).

An object of the invention is to avoid the drawbacks of the aforedescribed known solutions and to provide a disconnecting device for compressed-gas insulated switch installations which satisfies the requirements imposed on such installations in all respects.

The present invention provides a disconnecting device with two electrically series-connected movable contacts forming a double disconnect section, for compressed-gas insulated switch installations whose casing is composed of tubular elements, in which device a central member of the double disconnect section contains the two movable disconnecting elements, is held by an insulator forming a gastight bulkhead, and is accommodated in a section of the casing, whilst two fixed contacts are located in the adjacent sections of the casing for cooperation with respective movable contacts that each of the two disconnecting gaps constituted by a fixed and a movable contact being dimensioned for the full rated isolation voltage.

Advantageously, an earthing device is provided on the casing section accommodating the said central member, enabling the movable contacts to be earthed in the open position. This earthing device may be so constructed, as shown, for example, in 11.8. Pat. No. 3,356,798 to McKinnon, that earthing necessarily occurs when the disconnecting position is reached The length of the movable and fixed contacts and their arrangement are preferably so selected, that when in the open position the contacts do not project beyond the ends of the casing sections. Moreover, at least one of the fixed contacts may be held in the casing by an insulator which forms a bulkheadwall. The movable contacts may be actuated by means of two cranks driven by a commonshaft, which are in dead center position at each end of their movement. The gastight sealing of the bulkhead wall of the central member may become elfective only in the open position or in the dismantled position of .the contacts, thereby avoiding wear on the sealing element during operational switching.

The invention will now be described with reference to the accompanying diagrammatic drawing, which illustrates an exemplary embodiment of the invention, in longitudinal section. Reference numeral 1 designates a tubular portion of the metallic casing of a switch installation, which is joined to the two adjacent metallic casing portions 2 and 3. The hollow interior of casing section 1 contains and supports two oppositely movable solid cylindrical disconnecting contact members 4 and 5 and which are gastight sealed within member 1 as at 14 and 15 and are electrically connected in series and mounted on the longitudinal axis of the tubular casing l by means of an insulator 6 forming a bulkhead wall. The movable disconnecting contact members 4 and 5, shown in the open position, are moved longitudinally of themselves to the open or closed position by means of a rotatable shaft 7 coupled to the contacts via two cranks 8 and 9 respectively, which are in dead center positions in both the open and the closed position of the contact members.,The two contact members 4 and 5, when moved into the closed position, engage respectively in stationary contact members 10 and 11, which are correspondingly arranged in the adjacent tubular metallic casing sections 2 and 3 joined to opposite ends of the tubular casing 1. Each of the two pairs of contact members 4,10 and 5,11 is dimensioned for the full isolation voltage. Reference numeral l2designates an earthing device, with the aid of which the metallic central member 1' of the disconnecting device is earthed in the open position of the two contact members 4 and 5. Reference numeral 13 designates an insulator, which seals off the casing section 2 and also accommodates the fixed contact 10. However, this insulator 13 which is similar in structure to the insulator 6 need not be a bulkhead insulator, because the sealing by means of the bulkhead insulator 6 is in itself sufficient. The insulator 13 only serves as a further subdivision of the overall switch housing structure.

The disconnecting device described has a number of advantages. For example, it is so dimensioned that it can be accommodated in a casing similar to that of the rest of the installation. This casing is composed of tubular components, and the disconnecting device itself provides a simple seal for the compressed gas. By reason of its advantageous construction, the disconnecting device is easy to fit and to dismantle, and the mounting and/or dismantling of the adjoining parts of the installation is similarly facilitated. in addition, it offers the possibility of earthing the central portion of the double disconnect section with the aid of a simple device as soon as disconnection is completed.

The arrangement as a whole in turn ofi'ers substantial advantages from the operational and servicing point of view. Thus, the feature whereby one side of the disconnecting device can be serviced after evacuation of the compressed gas while the other side is still carrying voltage constitutes a substantial simplification. The individual disconnecting gaps can only operate in the presence of the requisite gas pressure. By means of the bulkhead insulator and seals 14 and 15, during removal of the adjacent casing section the remaining gap is preserved fully efi'ective from the insulating point of view. In the embodiment shown in the drawing, this means that when, for example, casing section 2 is removed the gas pressure remains unchanged on the right-hand side of the insulator 6, and the gap between contacts 5,1 1 remains fully effective and able to withstand the entire voltage normally present across both gaps in series.

Further advantages of the disconnecting device described are that, when the central section 1' is earthed after disconnection, the safe disconnection andgmthingpequirmythe relevant regulations and standards specifications are fully assured, whilst simultaneously the capacitive discharge currents, which could flow through the still operative disconnect section, are dissipated to earth, and that there is no danger of contact with voltage-bearing components. Consequently, the required work on the disconnected part of the installation can be carried out without danger.

With regard to the assembly and dismantling of the installation, it is further useful that the breaker contacts do not project beyond the ends of the casing in the open position, as otherwise they would increase the space requirement and would interfere with the work being carried out.

An advantageous further subdivision of the gas filling can be cylindrical metallic central member 1 accommodated in the achieved if at least one of the fixed contacts is also held by a bulkhead insulator. It then the associated casing section has to be removed, this can be carried out without prior evacuation of the gas. The interchange of adjacent casing sections can therefore be effected more rapidly. Owing to the use of oppositely movable contacts and cranks operating with only a small amount of rotation, the disconnecting device can be accommodated in a tubular casing whose diameter and crosssectional form correspond to the casing of the busbar lead. The disconnecting device, by reason of its dimensions, fits advantageously into the installation.

I claim:

1. A disconnect switch structure for use with a compressedgas insulated switch installation comprising a tubular casing, an elongated tubular metallic support located within a section of said tubular casing, a pair of electrically connected and movable contact members arranged for longitudinal movement in opposite'directions through the opposite ends of said tubular support and in gastight sealed relation therewith, mechanical means for moving said movable contacts in their opposite directions, an insulator mounting said tubular support within said casing and between the ends of said tubular support and which forms also a gastight bulkhead, and a pair 2. A disconnect switch structure as defined in claim 1' wherein said section of said casing within which said movable contact members are located includes an earthing device by means of which said movable contact members can be earthed when disengaged from their respective stationary contact members.

3. A disconnect switch structure as defined in claim 1 wherein said movable contact members are completely contained in the opposite end walls of said tubular support when in their disengaged position.

4. A disconnect switch structure as defined in claim 1 wherein at least one of said stationary contact members is also supported by means of an insulator forming a bulkhead within said casing. 

1. A disconnect switch structure for use with a compressed-gas insulated switch installation comprising a tubular casing, an elongated tubular metallic support located within a section of said tubular casing, a pair of electrically connected and movable contact members arranged for longitudinal movement in opposite directions through the opposite ends of said tubular support and in gastight sealed relation therewith, mechanical means for moving said movable contacts in their opposite directions, an insulator mounting said tubular support within said casing and between the ends of said tubular support and which forms also a gastight bulkhead, and a pair of stationary contact members correlated respectively to said movable contact members, said stationary contact members being located in adjacent sections of said casing on opposite sides of said gastight insulator, and each said movable contact member and its associated stationary contact member being electrically designed for the full rated isolation voltage.
 2. A disconnect switch structure as defined in claim 1 wherein said section of said casing within which said movable contact members are located includes an earthing device by means of which said movable contact members can be earthed when disengaged from their respective stationary contact members.
 3. A disconnect switch structure as defined in claim 1 wherein said movable contact members are completely contained in the opposite end waLls of said tubular support when in their disengaged position.
 4. A disconnect switch structure as defined in claim 1 wherein at least one of said stationary contact members is also supported by means of an insulator forming a bulkhead within said casing. 